The present invention relates to an endoscope forceps used together with an endoscope for grasping or tearing off tissue or the like of an organism.
An endoscope forceps for grasping or tearing off tissue or the like of an organism is disclosed in, for example, EP 0484671B1 (the Jpn. Pat. Appln. KOKAI Publication No. 4-246344), the Jpn. Pat. Appln. SHUTSUGAN Publication No. 5-78253 or the like.
An endoscope forceps disclosed in EP 0484671B1 comprises a handle assembly, a body assembly and a device mechanism. The handle assembly is constructed from a stationary handle and a pivoting handle. The body assembly is constructed from an outer tubular member and an inner rod member, and is fixed to the handle assembly at an end thereof, wherein the inner rod member has a bearing surface and is slidably disposed in the outer tubular member. The inner rod member is adapted for sliding in response to a movement of the pivoting handle in a condition that the body assembly is fixed to the handle assembly. The device mechanism is constructed from one pair of jaws each of which has a cam surface to engage with the bearing surface of the inner rod member in a freely slidable manner and a support member to support the one pair of jaws. In such a structure, when the pivoting handle is moved, the inner rod member is slid relatively to the outer tubular member. Thereby, the bearing surface of the inner rod member and the cam surface of the device mechanism, which engage with each other, relatively slide in a longitudinal direction to make the one pair of jaws pivot (opened or closed).
The endoscope forceps disclosed in EP 0484671B1 has problems as shown below:
(1) the structure is complex, it is hard to attain a desired mechanical strength and its production cost is high; PA1 (2) since many sliding parts are included and in addition, sliding lengths are large, abrasion cannot be avoided, and especially in autoclave sterilization, since lubrication by fat and oil cannot be expected, movements are not smooth and thereby abrasion is accelerated; PA1 (3) when the jaws get opened, the base end sections of the jaws where cam grooves are formed protrude out beyond the outer diameter of the support member, therefore, the base ends of the jaws cannot be covered with an electrically insulating member, which causes a metal portion widely exposed at the fore end of the forceps, and furthermore which produces a fear of burning of an unintended portion in cauterization by means of high frequency heating; and PA1 (4) an opening/closing drive mechanism for the forceps is disposed inside the support member which is located closer to the base end of forceps than a pivoting axis thereof and therefore, the opening/closing drive mechanism is hard to be cleaned. PA1 (1) when the jaws c, c are perfectly opened, a link a protrudes out beyond an outer diameter of a sheath in which the operating shaft b is inserted, an insulating cover which covers the outer surface of the sheath cannot accordingly be extended up to the fore end of the forceps, for that reason a metal is exposed at the fore end of the forceps and there arises a fear to burn an unintended portion in cauterization by means of high frequency heating and a suture thread, besides, has a chance to catch the link a in a suture operation in which the suture thread is grasped by the jaws if the link a protrudes out beyond the outer diameter of the sheath; PA1 (2) the forceps opening/closing drive mechanism is disposed inside a support member located at a position closer to a base end than pivoting shafts of the jaws c, c, which makes it hard to clean the forceps opening/closing drive mechanism.
An endoscope forceps disclosed in the Jpn. Pat. Appln. SHUTSUGAN Publication No. 5-78253, on the other hand, are provided with a forceps opening/closing drive mechanism in the form of a quadric crank chain as shown in FIGS. 34 and 35. FIG. 34 shows a relation between an operating force F and a grasping force f in a condition where one pair of jaws c, c is perfectly closed. Since an angle of inclination of a link a is small, as shown in the figure, a component F' of a force F pulling an operating shaft b is small. Consequently, a component F" of the component F' in a rotational direction of a jaw c is also small and a moment M which rotates the jaw c is very small. As a result, the grasping force f at the fore end of the jaws c, c is very small.
FIG. 35 shows a relation between an operating force F and a grasping force f in a condition where one pair of jaws are perfectly opened. Since an angle of inclination of a link a is large, as shown in the figure, a component F' of a force F pulling an operating shaft b is larger than F. As a result, a component F" of the component F' in a rotational direction of a jaw c is also as large as the component F' since the component F" is oriented in nearly the same direction as the component F'.
Therefore, the endoscope forceps disclosed in the Jpn. Pat. Appln. SHUTSUGAN Publication No. 5-78253 has problems as shown below: